Symmetric coherent OFDMA-PON configuration with low-speed ONU-side

A method by an optical network unit ONU includes, for downstream transmission, using a first tunable laser for coherent detection on a sub-band basis to increase receiver sensitivity and reduce analog-to-digital conversion ADC and digital signal processor DSP requirements within the ONU, and for upstream transmission, using a second tunable laser and using an optical signal beating between the first and second tunable lasers to generate a tunable radio frequency RF signal source for upstream multi-band OFDMA signal generation thereby avoiding need for an otherwise more costly RF clock source within the ONU, enabling low-speed digital-to-analog conversion DAC operation and rendering the ONU colorless in both optical and radio frequency RF domains.